We (as all mammals and many other animals), for the most part, possess bilateral symmetry. This means that our left side and right side of the body are more-or-less identical, when viewed at from outside (symmetric positioning of ears, hands, legs and eyes etc):). Bilateral symmetry is supposed to be an evidence for complex (animal) life, as it requires complex bio-chemical processes to ensure the symmetry.
Certain microscopic fossils in China (width of a few hairs pressed together!) have turned out to be the oldest examples of such a bilaterian. The remarkable discovery pushes back the genesis of complex animal life by as many as 50 million years:D:D.

Vernanimalcula fossil (Courtesy Pharyngula)USC College paleontologist David J. Bottjer was among the group that discovered the fossils - period-sized blobs believed to have skimmed the ocean floor with suction-cup mouths some 580 to 600 million years ago. Looking like teensy gumdrops or squashed helmets, they contain tissue layers, a gut, mouth and anus.
Bottjer, in his Scientific American article, describes the fossils, which measure about 200 micrometers across. He and his team sliced the samples into thousands of see-through-thin layers and examined them under a microscope. Finally, among the 10,000 slides, the collaborators discovered 10 examples of the fossil type they had been seeking. After more months of painstaking analysis, the group confirmed the examples were fossils of miniscule bilaterian animals. They named the find Vernanimalcula, meaning small, spring animal. The name refers to the time they lived after glaciers covered the planet.
The discovery is crucial. It suggests that the earliest ancestors to modern-day animals developed before the Cambrian explosion. That so-called explosion period, 488 to 542 million years ago, envelops the time on Earth when most animal groups first appeared:).